1. Field of the Invention
This invention relates generally to devices and methods for perceiving quantitative and qualitative information. This invention relates more specifically to audible methods and techniques for perceiving information provided by instrumentation used in the nondestructive evaluation of materials.
2. Description of Related Art
Nondestructive evaluation (NDE) technologies such as ultrasonics, acoustic emission, electromagnetics, radiography, and others, all generally rely on some form of visual presentation of the inspection information to allow for the human interpretation of the data. It is usually up to the test operator to rapidly view and translate the graphic information presented to him in order to acquire an understanding of the physical characteristics of the material under test and to properly control the progression of the analysis.
One of the most common NDE technologies is the utilization of ultrasonic signals for the detection of cracks and other irregularities in materials. The information provided by ultrasonic NDE methods is typically in the form of a visual display on a cathode ray tube or on a computer video display screen. The operator of such a system must interpret the visual displays of frequencies, amplitudes, and time in a manner that allows him to locate, and to some extent describe, the characteristics of the cracks or other irregularities found within the material under test.
In ultrasonic NDE, the material being tested may be scanned by a test operator with transducers that receive and/or transmit an ultrasonic signal. The receivers may be coincidentally located with the transmitter or may be separate elements on the same or an adjacent surface. The operator, therefore, must correlate what he sees on a display with the location of the transducers at any particular instant, and with the expected propagation paths of the signal in the material. Subtle variations in the display and the rapidity with which the display changes often prevent the operator/technician from visually interpreting all of the information being provided.
Ultrasonic evaluation is one of the more frequently utilized NDE technologies, and is representative of the NDE technologies to which the present invention may apply. Ultrasonic methods are widely used to detect and determine the depth or size of cracks and other flaws within otherwise homogenous materials. One ultrasonic crack sizing method, called the Tip Diffraction method, relies on the detection of two time separated signals. A schematic diagram of a typical application of the Tip Diffraction method is seen in FIG. 2. A visual display of the reflected and diffracted signals received from such a crack is shown in FIG. 3. Normally a strong reflected signal is received from the base of the crack and a smaller diffracted signal is created by the tip of the crack. The time difference between the occurrences of these two signals is directly related to the depth of the crack by common physical and trigonometric relations. An inspector can visually use this nondestructive inspection information to detect and size a crack by observing the signal information received and presented in a traditional NDE manner.
Another common use of ultrasonic technology is the determination of material wall thicknesses where an inspector does not have access to both sides of the wall, as in pipelines, aircraft structures, or power plant components. An ultrasonic pulse may be directed through the thickness dimension of the material, and be reflected back by the opposite wall to be received by the transducer. A typical signal representation which shows signals for three different thicknesses is depicted in FIG. 5. FIG. 4 schematically shows the configuration of an apparatus suitable for this method of determining wall thicknesses. The thickness of the material directly related to the ultrasonic signal's transit time through the material, and the velocity of sound in the material. This technique is also useful for (but is not limited to) detecting internal flaws such as material inclusions, delaminations, cracks, porosity, etc.
Whereas much emphasis in the NDE field has been placed on creating various means for extracting information from materials, very little emphasis has been placed on creating suitable methods for test operators to rapidly and easily interpret the information provided by these high tech means. Most of the existing ultrasonic and other NDE technologies rely almost exclusively on the presentation of the information in graphic form. The greatest extent to which the utilization of the human auditory system is involved has been to incorporate audible alarm systems that may be triggered when some material characteristic is detected that is out of a predetermined set of bounds. Beyond utilizing alarms for detection purposes, there is very little, if any, application of the human auditory system to the analysis of the characteristics presented in the information gathered using NDE technologies.
In general, NDE technologies rely on the utilization of non-destructive acoustic and electromagnetic waves and fields to remotely sense and describe physical properties of materials without altering their functional or structural integrity. Though disparate in nature, both acoustic and electromagnetic waves and fields have common describable parameters that can be easily translated into corresponding parameters for an electrical signal. The process of converting the sound waves and electromagnetic waves and fields into electrical signals whose amplitudes, frequencies, and time characteristics are directly related to the amplitudes, frequencies and time characteristics associated with the sound waves and electromagnetic waves is quite common. This is the aspect of NDE technology that has received the most attention since its development. Very little progress has been made, however, in taking these electrical signals generated by NDE transducers and/or sensors, and converting them into a form, other than visual, that can be readily interpreted by a human test operator.
It is not uncommon to view a human individual's most valuable sensory device as the human optical system. This is perhaps why most NDE information is provided to a test operator in graphic form, because of the assumption that the human optical system will be the best means for assessing and interpreting the NDE information. overlooked in the NDE field, and perhaps lesser understood, is the ability of the human auditory system to receive and interpret information. While much progress has been made in the NDE field to gather evermore detailed information about the characteristics of a material, not enough attention has been focused on the development of a systematic approach to allow the NDE test operator to interpret that information with his additional physical senses. It is this latter focus that forms the basis of the present invention.